This invention relates to inertia switches.
Inertia switches fall into two main categories. A first type employs a spherical mass held in a stable position by gravity in a groove or between a pair of raised contacts which it bridges, an acceleration force of suitable magnitude applied to the switch causes the body to roll from its stable position thereby opening the circuit between the contacts or operating a switch by its subsequent movement. Examples of this type are shown in British Patent Nos. 1,440,771 and 1,440,772. A second type employs an inertial mass supported as a pendulum either suspended under gravity by a non-resilient cord or supported on a cantilever leaf spring. Examples of this second type are shown in British Patent Nos. 1,391,901 and 849,962.
Inertia switches of the first type require careful handling and setting up to ensure that the freely moving sphere is located correctly, and, as the range of operation is related to the mass of the sphere, the individual dimensions and overall size of the switch are limited by factors outside the control of the designer.
Similarly with switches of the second type even though the moving parts are restrained in their movement, the length of the pendulum or cantilever spring means that in general the dimensions of such switches are not under the control of the designer who may have only a limited volume, in other equipment, in which to place an inertia switch.